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MPPT 150/100 low and fluctuating power output

System has been running well and as expected since commissioned about 6 weeks ago. But for the last 3 days, the MPPT 100/50 output wattage is fluctuating and the level is much lower than expected.

The last three days have been overcast but in the past 6 weeks during similar overcast conditions the system has maintained a fairly consistent 100W to 200W PV output.

System has four Longi LRS 72HPH 550W Mono panels wired in parallel to the MPPT. The MPPT is charging a Volthium LiFePO 24VDC 200ah battery that connects to a Magnum Pure Sine Wave Inverter/Charger - MS4024PAE.

Here is a sample from Victron Connect. Output wattage fluctuates randomly from near 0 W to less than 140 W. When scanning, the MPPT seems to hit 600W (in one instance) but then returns to the fluctuating output.

I would appreciate any troubleshooting tips. I have already checked the PV wiring and connections.

Thank you

screenshot-2023-08-25-at-20038-pm.png


MPPT SmartSolar
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seb71 avatar image seb71 commented ·
What was the battery voltage and what was the PV voltage?

Any loads?

Battery SOC?

"Overcast" can mean very different conditions.

When there is clear sky, do you get the expected power?

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abegweit avatar image abegweit seb71 commented ·

Hi @Seb71 the inverter is powered on but there are no AC loads, so it is in search mode drawing less than 30W plus about 20W for the Cerbo and router. Here is a picture of graph from Victron connect showing PV (blue) and battery (orange) voltages.

screenshot-2023-08-25-at-40609-pm.pngBattery SOC is low just 8%, with voltage of 25.8V

I agree. overcast is ambiguous but I have a second Victron system operating with 2 km of this system. It is a similar 24V configuration with four 425W panels wired in parallel to a 100/50 MPPT. This is the output from that MPPT this morning:

screenshot-2023-08-25-at-40212-pm.png

And this is the output from the system in question over the same period:screenshot-2023-08-25-at-40241-pm.png

These are both remote systems and I am not there today. But I can tell from the nearby system that the sky was clear for brief periods between 10:30 and 11:00am. Three peaks are visible in the second screen shot showing the system in question, but their durations are much shorter.

Thank you

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screenshot-2023-08-25-at-40212-pm.png (267.2 KiB)
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screenshot-2023-08-25-at-40609-pm.png (167.6 KiB)
seb71 avatar image seb71 abegweit commented ·

Can you make a custom VRM graph with PV voltage and battery voltage?

With same scale for both.

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abegweit avatar image abegweit seb71 commented ·

@Seb71 Yes, see below please.

screenshot-2023-08-25-at-61221-pm.png

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screenshot-2023-08-25-at-61221-pm.png (165.1 KiB)
seb71 avatar image seb71 abegweit commented ·

Looks fine.

I would wait for clear sky and see if it generates the expected power or not in those conditions.

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abegweit avatar image abegweit seb71 commented ·

Hi @Seb71, I visited the site today (about a 3hr drive each way). Clear sky, full sun. Same issue with the fluctuating power output. that I noted during the last 3 days which were overcast I tested the MPPT with each PV module separately. Between each test, I isolated the MPPT from the battery and the PV to force a reboot. The MPPT operated in the same fashion (fluctuating output between zero and 150W) regardless of which module was feeding the MPPT.

So I opened the PV breakers for 3 of the 4 modules and swapped out the 150/100 with a 100/20 that I had brought with me. The 100/20 worked as expected outputting a consistent 450W when connected to a single module. I continued on and operated the 100/20 MPPT with each of the PV modules separately and in each test, it outputted 450W consistently.

I left the 100/20 installed with one PV module connected to it. While I figure out what to do with the 150/100. Will call my dealer on Monday to see what can be done. The 150/100 is only a couple months old so I am hoping I can get a replacement under warranty.

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seb71 avatar image seb71 abegweit commented ·
Yeah, it looks like the 150/100 MPPT is defective, so contacting the dealer, like you said, is the next step.


If you are still at the site, take the MPPT with you (to not have to go back to that site just for that).

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kevgermany avatar image kevgermany ♦♦ abegweit commented ·

Did you make any changes at the point where Solar voltage and battery voltage switched?

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abegweit avatar image abegweit kevgermany ♦♦ commented ·
@kevgermany no changes made.
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